Five types of sensory receptors, each responding to a different type of stimulus, have been identified.

• Chemoreceptors—Respond to chemical compounds such as odor molecules
• Photoreceptors—Respond to light
• Thermoreceptors—Respond to changes in temperature
• Mechanoreceptors—Respond to changes in pressure or movement
• Pain receptors—Respond to stimuli that result in the sensation of pain